Multicore delivers multi-gigabits over microwave links

Fiber-optic cables are overkill for systems that don't need full throttle of fiber. Ceragon explains how it used multicore radio technology to boost capacity range of microwave transmissions.

While fiber-optic cable always holds an ultimate capacity advantage over microwave, a great many communication links don't require the full throttle of fiber. As lower-cost and quicker-to-deploy microwave technology increases in capacity, microwave becomes advantageous in more deployment scenarios heretofore addressable only by fiber. Breakthrough multicore radio technology now boosts microwave transmissions into the multi-gigabits-per-second capacity range where it has never ventured before, enabling system designers to use cost-effective microwave solutions that are considered too expensive to implement with fiber.

Multicore technology not only boosts capacity but increases link distance while decreasing power consumption and form-factor, further reducing total cost of ownership. Remotely configurable, multicore radios cut the operating expenses of transmission links today while assuring inexpensive network modernization in the future.

The architecture
The breakthrough multicore radio architecture is based on an advanced parallel radio processing engine built around Ceragon's in-house baseband modem and RFIC chipsets. Optimized for the processing of multiple radio signal flows, the architecture multiplies the capacity and increases the system gain over current technology. Using common processing resources at the kernel of the radio terminal, the multicore system reduces power consumption and maintains a small form-factor, making it especially attractive in numerous network backhaul scenarios, such as fronthaul and small-cell backhaul.

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A parallel radio processing engine differentiates multicore radios from other compact multi-carrier solutions that are really nothing more than multiple radio systems compacted into a single box. These do not offer the many benefits of the centralized resources of multicore technology.

Flexible operating modes
Multicore radio technology is inherently versatile and suitable for many different deployment scenarios. The multicore radio can operate initially as a high-capacity, single-core solution to suit a host of today's transmission requirements. As network evolution warrants, the second core can be activated remotely for optimized performance in myriad additional applications to fit virtually any backhaul, fronthaul, or other deployment scenario at far higher microwave capacities than ever before.

Basic performance: To illustrate, consider a generic, 1+0 single-core radio with high performance in terms of capacity, link distance, and antenna size:

Operating in single-core mode, the radio will have similar performance to the standard, but it will provide additional capacity due to its advanced modulation (2048QAM).

Doubling the capacity: Turning on the second core automatically doubles the bandwidth of the single-core radio (whether we use an adjacent frequency channel or the same one with orthogonal polarization, such as XPIC). This significant capacity boost is achieved without compromising system gain or availability—since it comes about from the use of an additional carrier at the same modulation and same Tx power and Rx sensitivity—while maintaining the same small form-factor. Effectively, it is a pure doubling of capacity without any trade-offs.

Doubling the link distance: The multicore radio can also be leveraged to increase link distance. In our implementation, the FibeAir IP-20C, the multicore equipment splits the transmitted bitstream between its two cores using Multi-carrier Adaptive Bandwidth Control, which, in turn, makes possible a lower modulation scheme that significantly increases system gain (both higher Tx power and lower Rx sensitivity). Increased system gain contributes to greater signal distance. The multicore radio can achieve significantly longer link spans even up to double the distance.

For example, let's consider a case where the multicore radio, in 1+0 configuration (only one core is activated), transmits 260Mbps with 2048QAM modulation over a 28MHz channel. Activating the second core makes it possible to reduce the modulation to 64QAM and yet transmit more capacity: 280Mbps (2 X 140Mbps over the 28 MHz channel). Reducing the modulation from 2048QAM to 64QAM also delivers a 4dB improvement in Tx power and a 15dB improvement in Rx sensitivity yielding an overall increase of 19dB in system gain. With this improvement, we can double the distance of the link and, at the same time, enjoy an additional 20Mbps of overall capacity.

Halving the antenna size: The system-gain boost enabled by the multicore radio can be leveraged to scale down the antenna size. A radio rule of thumb dictates that every doubling of antenna size on one side of the link translates into 6dB more link budget. The 19dB boost to system gain, as described in the example above, can be exploited to halve the antenna size (using 12dB of the 19dB gain) on each side of the link, still leaving 7dB which can be used to further reduce antenna size on either side. Smaller antennas cost less and require less space, so the network operator enjoys CAPEX savings from the multicore deployment and OPEX savings due to lower tower-leasing fees.